Field of Invention
The present invention relates to bonding a wafer of semiconductor light emitting devices to a substrate.
Description of Related Art
Semiconductor light-emitting devices including light emitting diodes (LEDs), resonant cavity light emitting diodes (RCLEDs), vertical cavity laser diodes such as surface-emitting lasers (VCSELs), and edge emitting lasers are among the most efficient light sources currently available. Materials systems currently of interest in the manufacture of high-brightness light emitting devices capable of operation across the visible spectrum include Group III-V semiconductors, particularly binary, ternary, and quaternary alloys of gallium, aluminum, indium, and nitrogen, also referred to as III-nitride materials. Typically, III-nitride light emitting devices are fabricated by epitaxially growing a stack of semiconductor layers of different compositions and dopant concentrations on a sapphire, silicon carbide, III-nitride, or other suitable substrate by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxial techniques. The stack often includes one or more n-type layers doped with, for example, Si, formed over the substrate, one or more light emitting layers in an active region formed over the n-type layer or layers, and one or more p-type layers doped with, for example, Mg, formed over the active region. Electrical contacts are formed on the n- and p-type regions.
FIG. 6 illustrates an LED die 4 bonded to a transparent lens 2, described in more detail in U.S. Pat. No. 7,053,419. LED die 4 includes a first semiconductor layer 80 of n-type conductivity and a second semiconductor layer 100 of p-type conductivity. Semiconductor layers 80 and 100 are electrically coupled to active region 120. N-contact 140 and p-contact 160 are disposed on the same side of LED die 4 in a flip chip configuration. Transparent superstrate 340 is formed from a material such as, for example, sapphire, SiC, GaN, or GaP. Lens 2 is bonded with bonding layer 6 to transparent superstrate 340. Bonding layer 6 may be silicone. Bonding layer 6 may include luminescent material that converts light of wavelengths emitted by active region 120 to other wavelengths. The luminescent material may be conventional phosphor particles.